64 FLORA. 



Spikelets 6 mm. or less long. 



Spikelets readily deciduous at maturity. 



Empty scales not awned. 35. Alopecurus. 



Empty scales awned. 38. Polypogon. 



Spikelets not deciduous ; empty scales persistent. 



Flowering scales slightly exceeding the empty ones. 



33. Heleochloa. 

 Flowering scales much shorter than the empty ones. 



34. Phtenin. 

 Spikelets 10-12 mm. long; tall seashore grasses. 43. Ammcphila. 



Spikelets variously panicled ; panicle not spike-like, except in a few species of No. 37. 

 Seed loosely enclosed in the pericarp, which opens readily at maturity. 

 Empty scales minute ; low arctic grass. 36. Pltippsia. 



Empty scales not minute ; no callus, awns or hairs. 37. Sporobolus. 

 Seed adherent to the pericarp. 



Palet i -nerved ; stamen i ; flower plainly stalked : scales not hairy. 



40. Cinna. 

 Palet 2-nerved ; stamens 3; flower not plainly stalked. 



Flowering scale bifid, with a delicate awn on its back ; rachilla prolonged 



into a short bristle. 45. Apera. 



Flowering scale entire ; rachilla not prolonged into a bristle. 



Callus with a tuft of long hairs at the base (except in some species 



of genus 42.) 



Rachilla extended beyond the palet. 42. Calamagrostis. 



Rachilla not extended beyond the palet. 44. Calamovilfa. 

 Callus naked or with very short hairs. 



Empty scales somewhat shorter than the flowering ones ; arctic 



grass. 39. Arctagrostts. 



Empty scales longer than the flowering ones ; panicle open ; 

 spikelets small. 41. Agrostis. 



Tribe VIII. AVENEAE. 



Spikelets deciduous ; lower flower perfect, upper staminate, awned : plant velvety. 



46. Holcus. 

 Spikelets not deciduous ; empty scales persistent, flowering ones deciduous. 



Spikelets of 2 perfect flowers ; rachilla not prolonged beyond the upper one. 



47. Aira. 

 Spikelets 2-many-flowered ; rachilla prolonged beyond the upper flower. 



Awn of flowering scale upon the back, inserted below the teeth. 

 Flowers all perfect, or the upper ones staminate or wanting. 

 Spikelets less than 12 mm. long ; grain free, unfurrowed. 

 Flowering scale finely erose-dentate or 2-lobed. 



48. Deschampsia. 



Flowering scale cleft or 2-toothed, with the teeth sometimes pro- 

 duced into awns. 49. Trisetum. 



Spikelets over 12 mm. long; grain furrowed, usually adherent to the 



scales. 50. Avena. 



Upper flower perfect, lower staminate, its scale strongly awned. 



51. Arrhenatherum. 

 Awn from between the lobes or teeth of the flowering scale, generally twisted. 



52. Danthonia. 



Tribe IX. CHLORIDEAE. 



Flowers perfect or some of them rudimentary. 



i perfect flower in each spikelet ; sometimes 2 in Nos. 59 and 61. 

 No empty scales above the flower. 

 Spikelets deciduous. 



Rachis produced beyond the upper spikelet ; spikelets narrow. 



54. Spartina. 

 Rachis not so produced ; spikelets globose, sometimes 2-flowered. 



61. Beckmannia. 



Spikelets not deciduous ; empty scales persistent ; low slender grasses. 

 Spikes 2-6, slender, digitate, 2.5-5 cm. long. 53. Capriola. 



Spikes many along a common axis, 5-10 cm. long. 



58. Sckedonnardus* 



